Dear Maintainer, Tests fail in restricted or containerized build environments where cgroup process tree memory accounting is restricted or returns 0. Specifically `ChildMemoryTest` fails because `memory_used_by_process_tree_rooted_at` returns <= 0. I have attached a patch (0018-skip-memory-tests-containers.patch) that checks if memory tracking is functional in `setUpClass` and skips the test if it is unavailable, rather than failing the build. This is currently applied downstream in Ubuntu. (LP: #2169491).